#define _CRT_SECURE_NO_WARNINGS  1
#include <math.h>
#include <stdio.h>

int main() {
    int r, x, y, x1, y1;
    while (scanf("%d%d%d%d%d", &r, &x, &y, &x1, &y1) == 5)
    {
        int t = 0;
        t = pow((pow((x1 - x), 2) + pow((y1 - y), 2)), 0.5);
        int k = 0;
        k = t / (2 * r);
        if (t % (2 * r)) {
            k = k + 1;
        }
        printf("%d\n", k);
    }
    return 0;
}